$$$- 2 e^{t} \sin{\left(t \right)}$$$の導関数

定数倍の法則 $$$\frac{d}{dt} \left(c f{\left(t \right)}\right) = c \frac{d}{dt} \left(f{\left(t \right)}\right)$$$ を $$$c = -2$$$ と $$$f{\left(t \right)} = e^{t} \sin{\left(t \right)}$$$ に対して適用します:

$${\color{red}\left(\frac{d}{dt} \left(- 2 e^{t} \sin{\left(t \right)}\right)\right)} = {\color{red}\left(- 2 \frac{d}{dt} \left(e^{t} \sin{\left(t \right)}\right)\right)}$$

積の微分法 $$$\frac{d}{dt} \left(f{\left(t \right)} g{\left(t \right)}\right) = \frac{d}{dt} \left(f{\left(t \right)}\right) g{\left(t \right)} + f{\left(t \right)} \frac{d}{dt} \left(g{\left(t \right)}\right)$$$ を $$$f{\left(t \right)} = e^{t}$$$ と $$$g{\left(t \right)} = \sin{\left(t \right)}$$$ に適用する:

$$- 2 {\color{red}\left(\frac{d}{dt} \left(e^{t} \sin{\left(t \right)}\right)\right)} = - 2 {\color{red}\left(\frac{d}{dt} \left(e^{t}\right) \sin{\left(t \right)} + e^{t} \frac{d}{dt} \left(\sin{\left(t \right)}\right)\right)}$$

指数関数の微分は$$$\frac{d}{dt} \left(e^{t}\right) = e^{t}$$$です:

$$- 2 e^{t} \frac{d}{dt} \left(\sin{\left(t \right)}\right) - 2 \sin{\left(t \right)} {\color{red}\left(\frac{d}{dt} \left(e^{t}\right)\right)} = - 2 e^{t} \frac{d}{dt} \left(\sin{\left(t \right)}\right) - 2 \sin{\left(t \right)} {\color{red}\left(e^{t}\right)}$$

正弦関数の導関数は$$$\frac{d}{dt} \left(\sin{\left(t \right)}\right) = \cos{\left(t \right)}$$$:

$$- 2 e^{t} \sin{\left(t \right)} - 2 e^{t} {\color{red}\left(\frac{d}{dt} \left(\sin{\left(t \right)}\right)\right)} = - 2 e^{t} \sin{\left(t \right)} - 2 e^{t} {\color{red}\left(\cos{\left(t \right)}\right)}$$

簡単化せよ:

$$- 2 e^{t} \sin{\left(t \right)} - 2 e^{t} \cos{\left(t \right)} = - 2 \sqrt{2} e^{t} \sin{\left(t + \frac{\pi}{4} \right)}$$

したがって、$$$\frac{d}{dt} \left(- 2 e^{t} \sin{\left(t \right)}\right) = - 2 \sqrt{2} e^{t} \sin{\left(t + \frac{\pi}{4} \right)}$$$。